Catheters are used for an ever-growing number of medical procedures including diagnostic and/or therapeutic procedures. To facilitate placement of the diagnostic and/or therapeutic catheter at a location of interest within a patient, a catheter may be introduced through a second catheter, which is commonly known as a “sheath” or “introducer catheter,” and these two terms will be used interchangeably herein. An introducer catheter is a tube that is used to facilitate the placement of other catheters into specific areas of the patient's body. In the field of cardiac ablation, for example, introducer catheters may be used to negotiate the patient's vasculature such that an ablation device may be passed through and positioned to be able to ablate arrhythmia-causing cardiac tissue. The introducer catheter itself may be advanced over a guidewire.
Complex coronary anatomy including tortuosity, calcification, as well as other structural characteristics of the coronary artery can make transit of hardware through the lumen proximal to a stenosis difficult and sometimes impossible. Several advancements in technology such as stiffer guidewires, large bore guide catheters that allow for improved passive support, and hydrophilic coatings that provide reduced friction, have improved the ability to advance balloons and stents through these coronary arteries with some success. Guidewires that allow for dynamic deflection of the tip such as the “Wiggle” wire have also improved hardware transit. However, even with these advances, in view of the expanding indications for percutaneous coronary intervention (“PCI”), there is an unmet need for improving PCI outcomes in complex substrates.
A guide catheter may be located inside an introducer catheter, and an inner support catheter (“daughter” or “child” catheter) placed inside a guide catheter. Advancing the inner support catheter into the coronary artery deeply intubating the proximal coronary-artery lumen has been shown to improve support of the guide catheter and inner catheter composite system, thereby providing an opportunity for improved success for device advancement through a difficult coronary lumen (Guideliner, Guidezilla, Telescope). Frequently, these inner catheters are only able to navigate the proximal simpler portions of the artery anatomy, and do not allow the operator to obtain a position in the artery lumen that provides sufficient support to the guide catheter and inner catheter composite system. The inability to advance these inner catheters further into a patient's vasculature is frequently as a result of the “razor effect” caused by an overhang or transitions between the guidewire and the inner-support catheter.
Generally, it is known that the introducer catheter must have an overall diameter small enough to negotiate through a lumen of a vessel while retaining an inner diameter (or “bore size”) large enough to accommodate a diagnostic, a therapeutic and/or an ablation device therethrough. Furthermore, since the path within a patient's vessel is often long and tortuous, steering forces must be transmitted over relatively long distances. Accordingly, it is desirable for the introducer catheter to have enough axial strength to be pushed through the patient's vasculature via a force applied at its proximal end (“pushability”). It is also desirable for the introducer catheter to be capable of transmitting a torque applied at the proximal end through to the distal end (“torqueability”). An introducer catheter should also have enough flexibility to conform substantially to the patient's vasculature and yet resist kinking as it conforms to the patient's vasculature. These various characteristics are often in conflict with one another, with improvements in one often requiring compromises in others. For example, increasing the bore size of an introducer catheter having a given overall diameter requires utilizing a thinner wall. As catheters are used in smaller and smaller passages and vessels, there is a growing need to use introducer catheters that have a smaller outer dimension. However, a thin-walled introducer catheter is more likely to collapse upon itself or kink when a torque or a push force is applied at its proximal end.
In order to facilitate the advancement of an introducer catheter (or an introducer sheath) through a patient's vasculature, the application of a push force and/or torque at the proximal end of the introducer catheter and the ability to orient selectively the distal tip of the introducer catheter in a desired direction can permit medical personnel to advance the distal end of the catheter and to position the distal portion of the introducer catheter at a location of interest.
During use, an introducer catheter shaft should be capable of transmitting torque and resisting compression. Substantial frictional forces sometimes resist transmission of axial forces and torque along the length of the introducer catheter. In some cases, these forces may cause the introducer catheter shaft to twist about a longitudinal axis of the introducer catheter shaft, storing energy in the process in a spring-like fashion. If such energy is released suddenly, the distal end of the introducer catheter, which may have been deflected by a steering mechanism, may be undesirably propelled with significant force.
With respect to resisting compression during use, it is important that users be able to advance the introducer catheter through a vessel, sometimes against significant frictional resistance, without undue axial or radial compression or snaking or fish-mouth distortion of the introducer catheter shaft. Shaft compression may complicate the positioning of the distal end of the introducer catheter shaft at a desired location for a medical procedure. In addition, medical personnel may rely on tactile feedback to attain and verify proper positioning of the introducer catheter, and such feedback can be impaired by excessive compressibility.
Accordingly, there is a need for improved devices, systems and methods to deliver an introducer catheter or a sheath or a guide catheter or an inner catheter at a location of interest within a patient's body via a body lumen without damaging the lumen, or a body vessel, including a tortuous lumen or vessel. The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal or limitation of claim scope.